Inoue et al. (A. Inoue, T. Zhang, T. Masumoto “Preparation of Bulky Amorphous Zr—Al—Co—Ni—Cu Alloys by Copper Mold Casting and Their Thermal and Mechanical Properties,” Materials Transactions JIM 36(3), 391-398 (1995)), the disclosure of which is incorporated herein by reference in its entirety, discloses Zr—Co—Ni—Al metallic glass-forming alloy systems with compositions (subscripts denote atomic percentages) Zr60Al10(Co—Ni)30, Zr60Al15(Co—Ni)25, and Zr55Al20(Co—Ni)25. The disclosure teaches that bulk glass formation (i.e. where a glass part having cross section thickness in excess of 1 mm can be formed) is not possible in the Zr60Al10(Co—Ni)30 system, and is possible in the Zr60Al15(Co—Ni)25 and Zr55Al20(Co—Ni)25 systems only when the Co atomic fraction is less than 10 percent.
Li et al. (Y. H. Li, W. Zhang, C. Dong, A. Makino “Effects of Cu, Fe, and Cu Addition on the Glass Forming Ability and Mechanical Properties of Zr—Al—Ni Bulk Metallic Glasses,” Science China 55(12), 2367-2371 (2012)), the disclosure of which is incorporated herein by reference in its entirety, discloses Zr—Co—Ni—Al metallic glass-forming alloys with composition (subscripts denote atomic percentages) Zr60CoxNi25-xAl15Ti4, where the atomic concentration of Co, x, ranges from 0 to 10%. The disclosure reports that the alloys are capable of forming ribbons with thickness of 20 micrometers. The critical rod diameter of the alloys is not reported, however, it is noted to be less than 15 mm.